The present disclosure relates to data storage systems, and more specifically, to migrating data within data storage systems.
A data storage system can have one or more storage tiers in one or more storage devices. Tiered storage is a data storage environment consisting of two or more kinds of storage delineated by differences in at least one of these four attributes: price, performance, capacity and function. Any significant difference in one or more of the four defining attributes can be sufficient to justify a separate storage tier.
Extents can be managed on tiered storage. An extent is a contiguous area of storage in a computer file system, reserved for a file. When a process creates a file, file-system management software allocates a whole extent. When writing to the file again, possibly after doing other write operations, the data continues where the previous write left off. This can reduce or eliminate file fragmentation and possibly file scattering too. An extent-based file system (i.e., one that addresses storage via extents rather than in single blocks) need not require limiting each file to a single, contiguous extent.